1. Field of the Invention
An aspect of the present invention relates to a hard disk drive, and more particularly, to a method and an apparatus to control changes in a flying height between a write head and a disk caused by a write current or an overshoot of a write current.
2. Description of the Related Art
Depicted in FIG. 1 is a protrusion of a write pole caused by magnetic fields generated between a head and a disk when a write current is provided. The bar on the right-hand side of FIG. 1 shows that the protrusion becomes more serious as the flying height between the head and the disk increases. Accordingly, in situations where the head flies and serious protrusion occurs, contact between the head and disk also takes place causing the interface between the head and a medium to be seriously affected.
Generally, a hard disk drive comprises at least one rotating disk or platter whose surface is coated with magnetizable material. Even when a flying height from the surface of each platter is maintained, if a write current is provided to a related read/write head, a pole tip forming the head exhibits characteristics of thermal expansion in accordance with Joule's heat by a normal state value and an overshoot value of a transient state of the write current. Consequently, due to thermal expansion, the protrusion of the write pole shown in FIG. 1 and contact between the head and disk occurs, reducing the reliability of the write operation.